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<h2><span class="refentrytitle">Struct async_handler</span></h2>
<p>boost::process::extend::async_handler</p>
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<h2 class="refsynopsisdiv-title">Synopsis</h2>
<div class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../../process/reference.html#header.boost.process.extend_hpp" title="Header &lt;boost/process/extend.hpp&gt;">boost/process/extend.hpp</a>&gt;

</span>
<span class="keyword">struct</span> <a class="link" href="async_handler.html" title="Struct async_handler">async_handler</a> <span class="special">:</span> <span class="keyword">public</span> boost::process::extend::handler,
                       <span class="keyword">public</span> boost::process::extend::require_io_context
<span class="special">{</span>
<span class="special">}</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="id-1.3.29.10.14.5.4"></a><h2>Description</h2>
<p>Inheriting this class will tell the launching function, that an event handler shall be invoked when the process exits. This automatically does also inherit <a class="link" href="require_io_context.html" title="Struct require_io_context">require_io_context</a>.</p>
<p>You must add the following function to your implementation:</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Executor</span><span class="special">&gt;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">function</span><span class="special">&lt;</span><span class="keyword">void</span><span class="special">(</span><span class="keyword">int</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&amp;</span><span class="special">)</span><span class="special">&gt;</span> <span class="identifier">on_exit_handler</span><span class="special">(</span><span class="identifier">Executor</span> <span class="special">&amp;</span> <span class="identifier">exec</span><span class="special">)</span>
<span class="special">{</span>
    <span class="keyword">auto</span> <span class="identifier">handler_</span> <span class="special">=</span> <span class="keyword">this</span><span class="special">-&gt;</span><span class="identifier">handler</span><span class="special">;</span>
    <span class="keyword">return</span> <span class="special">[</span><span class="identifier">handler_</span><span class="special">]</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">exit_code</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">error_code</span> <span class="special">&amp;</span> <span class="identifier">ec</span><span class="special">)</span>
           <span class="special">{</span>
                <span class="identifier">handler_</span><span class="special">(</span><span class="keyword">static_cast</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span><span class="special">(</span><span class="identifier">exit_code</span><span class="special">)</span><span class="special">,</span> <span class="identifier">ec</span><span class="special">)</span><span class="special">;</span>
           <span class="special">}</span><span class="special">;</span>

<span class="special">}</span>
</pre>
<p>The callback will be obtained by calling this function on setup and it will be invoked when the process exits.</p>
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<tr><td align="left" valign="top"><p>Cannot be used with boost::process::spawn </p></td></tr>
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<div class="copyright-footer">Copyright © 2006-2012 Julio M. Merino Vidal, Ilya Sokolov,
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